Mapping a textures z location from [0 to -40] to [0 - 1] for baking baking sound to f-curve
If I understand you correctly, you'd like to map the incoming 0-&gt;1 audio amplitude range from the baked f-curve, to a 0 -&gt; -40 range for use inside a shader node-tree.
You can key the incoming audio range into an Input &gt; Value  node, and map that to any other range you like with a Converter &gt; Map Range node:

... here, mapping  0 -&gt; 1 to 0 -&gt; -40, influencing only the Z-component of the location of the texture space. The 'Clamp' checkbox causes the output to flatline at the min and max of the ranges. If unchecked, the mapping extrapolates.
Using a Value node is more flexible than keying, say, the 'Fac' of a color-ramp directly. The single 0 -&gt; 1 audio input can be branched, and mapped to different ranges for different features of your tree.